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Factors affecting wollastonite carbonation under CO2 supercritical conditions



The feasibility of a carbon dioxide disposal method based on combining carbon dioxide chemically with silicate rocks was tested in this experiment. The process uses a stirred batch reactor, in which supercritical carbon dioxide is absorbed into a rock slurry to cause dissolution of the mineral and precipitation of calcium carbonate. Wollastonite (CaSiO3) was chosen in a systematic study because it had the highest conversion among the rocks investigated in a preliminary test. The effects of operating variables—including reaction time, reaction pressure, the particle size of wollastonite, reaction temperature, and solution composition—on the conversion of wollastonite were investigated, and a reaction mechanism was proposed to explain these effects. The conversion was determined by means of thermogravimetric analysis. A high conversion of 90% was achieved by using a solution composed of 1 M NaHCO3 to prepare the wollastonite slurry when the carbonation reaction was operated at 8.6 MPa and 383 K for 6 h. © 2005 American Institute of Chemical Engineers AIChE J, 2006